The coupling of lithium metal-terminated polymers is a process known in the art. In accordance with this known process, a lithium metal-terminated polymer is treated with a compound having two or more functional groups containing two or more reactive sites capable of reacting with the carbon-lithium metal bonds of the lithium metal-terminated polymer. In many cases the multifunctional coupling agent thereby becomes a nucleus for the resulting structure. From this nucleus long chain polymeric branches radiate and such coupled polymers have specific properties that render then useful for particular applications.
A wide variety of coupling agents are known. U.S. Pat. No. 3,244,664 discloses the use of certain silicic compounds including silicon tetrachloride and a limited group of silanes and siloxanes. U.S. Pat. No. 3,281,383 discloses the use of multifunctional coupling agents having three or more reactive sites. The types of multifunctional coupling agents disclosed therein include polyepoxides, polyisocyanates, polyimines, polyaldehydes, polyketones, polyanhydrides, polyesters, polyhalides and mixtures thereof. Similar coupling agents are disclosed in U.S. Pat. No. 3,468,972. The use of silicic coupling agents are further disclosed in U.S. Pat. No. 3,692,874 and U.S. Pat. No. 3,880,954. The latter patent is specifically concerned with the use of a trimethoxymethyl silane coupling agent. A novel coupling agent has now been found that combines a high coupling efficiency with the ability to form both linear and radial polymers.